Eavesdropping acoustics

[Flame of Anor]

Is anyone else bothered by the idea that V's chamber would eavesdrop on the room above it? Surely a parabolic shape like that would collect sound from below. Like so (but rotated):

http://upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Parabolic_mirror-diagram.svg/319px-Parabolic_mirror-diagram.svg.png

[Ninja]

There might be a bunch of pipe-like tunnels implanted between the two rooms that help with the acoustics? I don't know, I'm not knowledgeable in architecture.

[Xelbiuj]

Is anyone else bothered by the idea that V can toss fireba. . . you get the idea.

Anything in fantasy fiction that sounds almost remotely plausible is possible.
Why not mention the impossible buoyancy of Julio Scoundrel's airship?

[Defiant]

I would not expect the author of this comic to be a keen mathematician or physicist, nor would I care if he is. I come here to be entertained by a good story. If you'll notice, Vaarsuvius never mentioned anything about a parabolic arc, and the visual representation within the comic was likely merely to identify the change in location.

I fully expect anything that functions in the manner that chamber does to be sufficiently robust or magical in nature. I know of no "shape" in the real world that would be able to block all noise in one direction, but carefully amplify it in the other.

[Peelee]

Is anyone else bothered by the idea that V's chamber would eavesdrop on the room above it? Surely a parabolic shape like that would collect sound from below. Like so (but rotated):

http://upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Parabolic_mirror-diagram.svg/319px-Parabolic_mirror-diagram.svg.png

By Earthican physics, you would be correct. You are failing to account for the existence of magic and how it relates to physics in the OotS world. In this specific case, the parabolic shape lets sound in from above because shut up*, that's why.

*"shut up" is solely for comedic value. Please don't actually shut up. That was a good, well thought out question, and this is just how I see things. I'll change the wording if it offends.

[ClockShock]

disclaimer: This may well all be wrong, but no sound experts seem to be answering so you're getting me instead. This is how things work in my head:

My complete lack of Physics knowledge suggests that your diagram is the wrong way round (in that the sound waves are coming from the wrong direction, because we should be considering sound from above the room not within it).

Sound travels faster through solids than gases, so when the wave passes through the ceiling, then hits the curved surface, it bends inwards (the inner part of the wave hits the gas sooner, and slows, so that the wave bends towards the centre where V would be).

Kind of like the way light curves through refraction:
http://www.naturalpigments.com/education/images/light_refraction_2surface.gif

The reverse should happen from inside, so any sound V makes gets dispersed. Use some fantasy materials to exaggerate the effect, and hey-presto! eavesdropping chamber.

(Actually, as pointed out by posters below, even if this did hold it would also amplify any sound V makes into the chamber above.)

disclaimer: I'm still pretty much just making this up.

[Chronos]

Yeah, think lenses, not mirrors. Ordinarily, a converging lens will be convex, but since sound travels faster in stone than in air, you would want concave, like what's pictured here.

The only part that bothers me about it is that lenses work both ways. If the room makes it easier for V to hear Roy, it should also make it easier for Roy to hear V. But that's a detail which I can suspend.

[Vinsfeld]

As a physicist, the eavesdropping acoustics bothered me, at first. But then I thought: "Hey, it's a webcomic. The author doesn't need to know physics. And also, it's not our world. People cast spells there. So, maybe, this is the result of a spell of some sort."

I mean, it shouldn't be so hard to create a spell that can make the sound get into the tunnels, but hardly go out of it.

[Tock Zipporah]

Is anyone else bothered by the idea that V's chamber would eavesdrop on the room above it? Surely a parabolic shape like that would collect sound from below. Like so (but rotated):

http://upload.wikimedia.org/wikipedia/commons/thumb/8/8c/Parabolic_mirror-diagram.svg/319px-Parabolic_mirror-diagram.svg.png

Actually, the diagram you show here is exactly why the eavesdropping chamber WOULD work.

You're looking at the problem backwards. Instead of asking "Why does the parabolic dish help V hear what is in the room above?" you should ask "Why does the parabolic dish block the people above from hearing V down below?"

As your diagram shows, any sounds or speech in the underground chamber would be reflected back down. This would prevent the sound from effectively traveling into the chamber above.

Then, look at the chamber where the gate lies. (http://www.giantitp.com/comics/oots0892.html) That octagonal room essentially has a similar dome-type shape inside.

http://i1230.photobucket.com/albums/ee496/equilibrate/Doubleparabolicchamber_zpsfcc2f913.png (http://s1230.photobucket.com/user/equilibrate/media/Doubleparabolicchamber_zpsfcc2f913.png.html)

The gate chamber is essentially one acoustic chamber mounted atop another. In both chambers, all sound is reflected downward. Sound from the gate chamber is reflected down to the listening chamber. Sound from the listening chamber is also reflected down, into the floor. This would allow the person in the listening chamber to hear what is going on above them, without allowing their voice to be transmitted back above.

[Cizak]

So am I the only one wondering if Rich is laughing his behind off or just drove his palm through the back of his skull right now?

[Flame of Anor]

Sound travels faster through solids than gases, so when the wave passes through the ceiling, then hits the curved surface, it bends inwards (the inner part of the wave hits the gas sooner, and slows, so that the wave bends towards the centre where V would be).

That's a cool and rather plausible explanation. However, as Chronos points out, you're incorrect in saying that it would be one-way.


You're looking at the problem backwards. Instead of asking "Why does the parabolic dish help V hear what is in the room above?" you should ask "Why does the parabolic dish block the people above from hearing V down below?"

...

The gate chamber is essentially one acoustic chamber mounted atop another. In both chambers, all sound is reflected downward. Sound from the gate chamber is reflected down to the listening chamber. Sound from the listening chamber is also reflected down, into the floor. This would allow the person in the listening chamber to hear what is going on above them, without allowing their voice to be transmitted back above.

Ooh, I really like this one. Good lateral thinking! I think yours is the only explanation that wouldn't necessarily require magical assistance/handwaving.


So am I the only one wondering if Rich is laughing his behind off or just drove his palm through the back of his skull right now?

:smallbiggrin:

[asphias]

great discussion so far.

another point i just thought of: anyone who has used a pitch fork with an acoustic guitar has probably noticed the giant difference between holding the pitch fork in the air, or putting it down on the soundboard of your guitar.
(if you have no clue what i'm talking about, try this: http://www.youtube.com/watch?v=zsZ76XdsCU4 )

so basically, the entire floor of the gateroom is used as a gigantic soundboard, with the people on it as the pitchfork. because people are standing on it while they talk, their sound vibrates the entire soundboard/floor, and thus produces sound in the chamber at the bottom.

V however, does not touch the roof/soundboard, and thus the sound goes through air before touching the soundboard, thus providing way less sound.

incidentically, the best way for V to get herself heard, was by actually touching the roof while screaming, and the soundboard would do the rest. notice how well the knocking works?:smallcool:

[TheYell]

If the intervening wall was solid and uniform, no. It should be two-way.

If it is a complex construct, with a conical void over the ceiling of V's auditorium, then a diaphragm in contact with the floor of the gate chamber could extend into the base of the conical void. Then, the diaphragm would vibrate with noise from the Chamber, the vibrations would be magnified by the cone, and be audible within V's auditorium. However there would not be any construct to magnify the vibrations of the diaphragm from sounds made on V's end.

It would be like an old-fashioned telephone with the speaking diaphragm removed. You could hear but not be heard.

*Unless you like, pounded on the whole thing with a magic fist.

[Rogar Demonblud]

I believe the construct is called The Laird's Ear, since it was prevalent in Scottish castles.

[Bulldog Psion]

I believe the construct is called The Laird's Ear, since it was prevalent in Scottish castles.

Laird's lug, actually. The only problem is that we don't know how the acoustics go in the other direction. It's quite possible that sound in the Lug would have been projected through the hall, too, and the skulking nobleman just concealed his presence by remaining silent.

[Flame of Anor]

I believe the construct is called The Laird's Ear, since it was prevalent in Scottish castles.

Sounds cool--source?

[Incom]

I only took a semester of acoustics and I don't think this is something we went over.

But if you shape the curve correctly, you can get all sound in an area to converge on one spot. And if the room is constructed correctly, that spot could be where V is sitting. If the room is an ellipse and the gate is one focus, all the sound would bounce directly to the eavesdrop room at the other focus. (Check the diagram for an ellipse on Wikipedia.)

I don't know how refracting through the floor might affect that, but considering Rich is likely not super versed in acoustics, he probably just approximated the effect anyway. But in principle, the room works fine.

[colanderman]

If it is a complex construct, with a conical void over the ceiling of V's auditorium, then a diaphragm in contact with the floor of the gate chamber could extend into the base of the conical void.

To illustrate, if I follow you correctly:


OotS
------------
\ /
\ /
\ /
\ /
\ /
__\/__
/ \
| V |
|______|

[karkus]

So am I the only one wondering if Rich is laughing his behind off or just drove his palm through the back of his skull right now?

Por que no los dos?

http://i.eho.st/pjsmnryj.jpg

[F.Harr]

I wasn't bothered by it. What do I know about accustics? I just like the story, I'm not going to let little things like improbability bother me. That's part of why I'm not a writer. That and a compleat lack of talent.



So am I the only one wondering if Rich is laughing his behind off or just drove his palm through the back of his skull right now?

Yes. Yes you are.


Actually, the diagram you show here is exactly why the eavesdropping chamber WOULD work.

You're looking at the problem backwards. Instead of asking "Why does the parabolic dish help V hear what is in the room above?" you should ask "Why does the parabolic dish block the people above from hearing V down below?"

As your diagram shows, any sounds or speech in the underground chamber would be reflected back down. This would prevent the sound from effectively traveling into the chamber above.

Then, look at the chamber where the gate lies. (http://www.giantitp.com/comics/oots0892.html) That octagonal room essentially has a similar dome-type shape inside.

http://i1230.photobucket.com/albums/ee496/equilibrate/Doubleparabolicchamber_zpsfcc2f913.png (http://s1230.photobucket.com/user/equilibrate/media/Doubleparabolicchamber_zpsfcc2f913.png.html)

The gate chamber is essentially one acoustic chamber mounted atop another. In both chambers, all sound is reflected downward. Sound from the gate chamber is reflected down to the listening chamber. Sound from the listening chamber is also reflected down, into the floor. This would allow the person in the listening chamber to hear what is going on above them, without allowing their voice to be transmitted back above.


great discussion so far.

another point i just thought of: anyone who has used a pitch fork with an acoustic guitar has probably noticed the giant difference between holding the pitch fork in the air, or putting it down on the soundboard of your guitar.
(if you have no clue what i'm talking about, try this: http://www.youtube.com/watch?v=zsZ76XdsCU4 )

so basically, the entire floor of the gateroom is used as a gigantic soundboard, with the people on it as the pitchfork. because people are standing on it while they talk, their sound vibrates the entire soundboard/floor, and thus produces sound in the chamber at the bottom.

V however, does not touch the roof/soundboard, and thus the sound goes through air before touching the soundboard, thus providing way less sound.

incidentically, the best way for V to get herself heard, was by actually touching the roof while screaming, and the soundboard would do the rest. notice how well the knocking works?:smallcool:


If the intervening wall was solid and uniform, no. It should be two-way.

If it is a complex construct, with a conical void over the ceiling of V's auditorium, then a diaphragm in contact with the floor of the gate chamber could extend into the base of the conical void. Then, the diaphragm would vibrate with noise from the Chamber, the vibrations would be magnified by the cone, and be audible within V's auditorium. However there would not be any construct to magnify the vibrations of the diaphragm from sounds made on V's end.

It would be like an old-fashioned telephone with the speaking diaphragm removed. You could hear but not be heard.

*Unless you like, pounded on the whole thing with a magic fist.

All plausable, especially when taken together, but I doubt it's a parabala, but some other complex shape. But I would wonder if and why he'd dug underneath the gate, but I suppose the rifts float at a specific relation to the mass of the world rather than being dragged towards the center of mass. 'Cause it's a rift rather than a thing.

[F.Harr]

disclaimer: This may well all be wrong, but no sound experts seem to be answering so you're getting me instead. This is how things work in my head:

My complete lack of Physics knowledge suggests that your diagram is the wrong way round (in that the sound waves are coming from the wrong direction, because we should be considering sound from above the room not within it).

Sound travels faster through solids than gases, so when the wave passes through the ceiling, then hits the curved surface, it bends inwards (the inner part of the wave hits the gas sooner, and slows, so that the wave bends towards the centre where V would be).

Kind of like the way light curves through refraction:
http://www.naturalpigments.com/education/images/light_refraction_2surface.gif

The reverse should happen from inside, so any sound V makes gets dispersed. Use some fantasy materials to exaggerate the effect, and hey-presto! eavesdropping chamber.

(Actually, as pointed out by posters below, even if this did hold it would also amplify any sound V makes into the chamber above.)

disclaimer: I'm still pretty much just making this up.

Also plausable when taken the other ideas. The quoting didn't work very well.

[Copperdragon]

Is anyone else bothered by the idea that V's chamber would eavesdrop on the room above it? Surely a parabolic shape like that would collect sound from below. Like so (but rotated):

The picture is not fitting, as the sound is coming from above. I assume it is more "magic" than actual physics.


disclaimer: This may well all be wrong, but no sound experts seem to be answering so you're getting me instead. This is how things work in my head:

No, this is bollocks. Sound works very different from light passing through different materials (which is what you basically posted).

As I wrote above this setup is not to be explained with physics.

[Flame of Anor]

The picture is not fitting, as the sound is coming from above.

If you mean the one I posted, that's just because I found it online and was too lazy to rotate and reupload it.


I assume it is more "magic" than actual physics.

Seems likely.

[Chronos]

Quoth Copperdragon:

No, this is bollocks. Sound works very different from light passing through different materials (which is what you basically posted).
Both are waves passing through different media with different wave speeds. The same physics applies to both. You'd only see a difference when it came to polarization, which exists for transverse waves like light, but not for longitudinal waves like sound.

[TheYell]

To illustrate, if I follow you correctly:


OotS
------------
\ /
\ /
\ /
\ /
\ /
__\/__
/ \
| V |
|______|

yes, except the cone would be inverted so it would work like a megaphone

[Bulldog Psion]

It's definitely magic. There's solid stone above that little chamber, with no opening at all depicted. No matter what the shape of the chamber, the sound waves aren't going to propagate through stone miraculously just because the top of the chamber is domed. There would have to be some kind of air access, and there isn't any.

So, it's 100% magic. Maybe just some kind of ensorcelled stone that transmits sound in one direction?

[pearl jam]

yes, except the cone would be inverted so it would work like a megaphone

Actually, I think that picture was fine. A megaphone disperses sound to a wide area, a cone like this collects it to a specific point, much like cupping your hand around your ear. In fact, people used to use small cones held to their ear as hearing aids.

[Cavenskull]

It's definitely magic. There's solid stone above that little chamber, with no opening at all depicted. No matter what the shape of the chamber, the sound waves aren't going to propagate through stone miraculously just because the top of the chamber is domed. There would have to be some kind of air access, and there isn't any.

So, it's 100% magic. Maybe just some kind of ensorcelled stone that transmits sound in one direction?

You don't need air for sound to propagate. Sound travels just fine down the string that tin can phones use, and I have no problems hearing the beeping of a waterproof wristwatch while submerged in a swimming pool. And then there's the well-known phenomenon of noisy neighbors being heard through the walls of apartments.

While the scenario presented in the comic may very well need magic in order to work, it's not because of the lack of air access.

[Bulldog Psion]

You don't need air for sound to propagate. Sound travels just fine down the string that tin can phones use, and I have no problems hearing the beeping of a waterproof wristwatch while submerged in a swimming pool. And then there's the well-known phenomenon of noisy neighbors being heard through the walls of apartments.

While the scenario presented in the comic may very well need magic in order to work, it's not because of the lack of air access.

Quite true. The shape is kind of a problem, though. It would tend to collect sound from below and focus it upward, rather than the other way around. See also the antique ear trumpet. That doesn't have the narrow end pointed outward and the belled end pressed against the head. :smallsmile:

[TheYell]

Good point about hearing trumpets. In fact that's an implement that carries the sound nearly at right angles. Maybe the void doesn't have to be symmetrical along an axis from source to audience to carry sound effectively.

I think we're at the point where we build some walls and find out :P

[F.Harr]

Good point about hearing trumpets. In fact that's an implement that carries the sound nearly at right angles. Maybe the void doesn't have to be symmetrical along an axis from source to audience to carry sound effectively.

I think we're at the point where we build some walls and find out :P

After that, we create a mould and fill it with cement and THEN we ding various stones to carve and possibly fit together based on their sound-propigating properties.

[Rogar Demonblud]

Sounds cool--source?

Many books on castle architecture and history, particularly Scottish. Apparently, people listening in became so prevalent the nobles had to do their scheming in taverns (http://en.wikipedia.org/wiki/Ainslie_Tavern_Bond).

[Copperdragon]

Both are waves passing through different media with different wave speeds. The same physics applies to both. You'd only see a difference when it came to polarization, which exists for transverse waves like light, but not for longitudinal waves like sound.

Sure, but the effect you oberserve in a elliptical cavity is not the same from both sides. On one side you have the reflection of sound when it is reflected on the stone and you get an amplification in the focus point.
From the other side, the sound goes from air to stone, and then to the air again. On this second transitition you do not get any aplification in the focus point.
So whatever might apply or now, I think the effect seen in the comic has not much to do with physics but with "magic".

[gorocz]

Quite true. The shape is kind of a problem, though. It would tend to collect sound from below and focus it upward, rather than the other way around. See also the antique ear trumpet. That doesn't have the narrow end pointed outward and the belled end pressed against the head. :smallsmile:

Right, think ear trumpet bug vastly bigger. The gate room is the wide end, the room where V is is a sort of a speaker attached to the narrow end, since you don't want the sound to be magnified the other way around as if you were standing inside a mouth-piece of a megaphone (like if you put a glass on the wall, it magnifies the sound from the other room too and not vice versa)

[Bulldog Psion]

Right, think ear trumpet bug vastly bigger. The gate room is the wide end, the room where V is is a sort of a speaker attached to the narrow end, since you don't want the sound to be magnified the other way around as if you were standing inside a mouth-piece of a megaphone (like if you put a glass on the wall, it magnifies the sound from the other room too and not vice versa)

Excellent point. :smallsmile:

[Amphiox]

Has anyone ever been to one of those ancient Greek theatres/stadiums? You can drop a coin on the stage, and everyone in the stands to the furthest row can hear it perfectly. But if you stand on the stage you cannot hear anything said out in the stands.

Similar effects can be experienced at any sports stadium or movie theatre.

That alone should tell people that this argument that "sound goes both ways" and that if you can hear on one end that means you must be able to be heard on both ends, is false.

It is quite possible to design acoustics that funnel sound waves in such a way as to make it so that sounds originating in location A are easy to hear in location B, but the reverse is not true.

[Amphiox]

With regards to the question of if this could just be magic, I would actually say that narratively this is unlikely.

Because the Draketooths are dead.

Nearly all the magic that used to permeate the pyramid is no longer active because all the Draketooths died. Only the most powerful magic like Girard's phantasm and the ring-trap around the Gate remained.

An effect of making it possible to hear in one place and not the other does not strike me as something that would require high-level magic, and instead seems like something that could easily be accomplished by a lower level spell, in which case it should not have endured with the Draketooths dying.

Furthermore, if it was a magic effect, V should have recognized that and made some comment about it.

So it seems more likely to me that this is a physical effect, just like the final double-bluff message.

[rodneyAnonymous]

It could be a permanent (http://www.dandwiki.com/wiki/SRD:Permanency) effect (something like mage's private sanctum (http://www.dandwiki.com/wiki/SRD:Mage%27s_Private_Sanctum)?) that does not require refreshing.

A combination of physical and magical effects seems probable.

[weeping eagle]

I think it's just a baby monitor, guys. They're like 15gp down at Wal-Mart.

[Copperdragon]

With regards to the question of if this could just be magic, I would actually say that narratively this is unlikely.

It is magic, because it's not physics. "Cheap" spells like that can easily be made to work in 100s of years.

[Boros Reckoner]

You know that old Indian trick where you hold your ear up to the ground and you can hear distant footsteps easier than if you were just standing up and listening to them?

This is because sound propagates through stone better than through air

So the sounds of the party above are being carried by the stone, and projecting out of the stone above V


Imagine the entire ceiling of the chamber V is in to be like a speaker

Now where would sound coming from the ceiling be most focused?

The bell shape would focus it towards V

The physics of the chamber is sound, pun intended

That being said, it is not okay to simply handwave it away is "well the author didn't know any better and its magic and its a comic and who cares anyway"

It is only the most hackneyed and amateur writers who require their readers to turn off their brains to be able to enjoy their work, we should expect more of OotS

[Copperdragon]

You know that old Indian trick where you hold your ear up to the ground and you can hear distant footsteps easier than if you were just standing up and listening to them?

That is because the foot lets the ground swing itself.


This is because sound propagates through stone better than through air. So the sounds of the party above are being carried by the stone, and projecting out of the stone above V

Yes, but you make one mistake: You neglect that the impulse if two particles hit is not well transferred from light to heavy. Compare this to throwing a ping pong ball at a truck or a walll. Air has a lot mass, stone a high one. We have a lot of stone there, so few soundwaves are going to transition from air to stone in the first wave.
Then the sound gets distorted in the stone as well. The waves at the top of the bell-cavity reach the stone-air-border much earlier than those that a transferred lower down in the bell. This means what you get once the stone is left and the waves become "sound" in the air again is very different from the initial signial that transitioned on a flat surface from air to stone.

What we see here is a very weakened, heavily distorted signal that might be loudest in the focus point, but I doubt it has much resemblence to the originial signal.



Imagine the entire ceiling of the chamber V is in to be like a speaker

No, I'm not. Because a speaker works differently.


The physics of the chamber is sound, pun intended

Yes, the pun is there, but the physics is not sound.


That being said, it is not okay to simply handwave it away is "well the author didn't know any better and its magic and its a comic and who cares anyway"

I'm handwaving it away because it's not working like that in real physics, especially if we see a thick wall of stone as we do. You simply do not hear normal speech through 30 cm of stone, no matter how the other side is formed.
Note the stone in itself is thick enough to even block Vaarsuvius from getting heard when screaming. There simply is no physical effect that enables this to work without "magic".


It is only the most hackneyed and amateur writers who require their readers to turn off their brains to be able to enjoy their work, we should expect more of OotS

Correct me if I'm wrong, but that was not the issue here. No one said it was "lazy writing" or "Switch of your brain!!1", the question is if that is actual physics or "pseudo-physics enhanced with magic". It is the latter and that is perfectly fine in a magical world.
It is also very fine in any other world that is not hardcore scifi (as in SCIENCE fiction) as it makes no difference at all why it works the way it does.

All I state is "This is not physics" and if you think it does, put in proof. I'm content with undergraduate level.

[Vinyadan]

Giantitp.com: overanalysis is our pride. Now with scientific baking!

http://s23.postimg.org/r4i9zhr5n/woman_baking_pie.jpg


Or was it backing? :smallannoyed: Damn, I forgot.

[Amphiox]

We do not actually know the exact shape of the upper chamber or the lower chamber, and we do not actually know the exact shape or composition of the layer of stone/earth/whatever that separates the two.

Without that knowledge it is in fact impossible to say whether or not the physics are sound.

Given what we do know, the only thing that can be said is that the physics are possible.

And since similar effects already exist in the real, non-magic world, and there is no reason to believe that the physics that govern sound are any different in the OotS world (everything shown in the comic concerning sound without magic works exactly as it does in the real world), there is no reason to assume that the effect in the comic is anything but non-magical.

It is more parsimonious to assume that the Draketooths would choose to design such a simple thing physically than waste any magic on it, particularly in a Vancian magic system.

[JustWantedToSay]

To hear something is not just about how much energy is transmitted, it's about where all reflections/refractions of the wave will reach the listener at close to the same time.

Sound travels much faster through stone than through air. When a sound is being transmitted to the chamber, it spreads all throughout the walls of that chamber, and then all of the walls/floor/and ceiling act as the apparent source.

To hear that sound clearly your ears need to be close to the centre, otherwise you'll still hear it, you just won't make out what it's saying.

Varsuvius' ears are a lot closer to the centre of her chamber, than the OOTS are to theirs.

IF the oots were somehow to manage to levitate to the centre of the room they could have heard V clearly. But otherwise, the shouting would have just been a incoherent hum.

[Flame of Anor]

That is because the foot lets the ground swing itself.

I'm not sure what this means.

[F.Harr]

I think it's just a baby monitor, guys. They're like 15gp down at Wal-Mart.

I love it!


Giantitp.com: overanalysis is our pride. Now with scientific baking!

http://s23.postimg.org/r4i9zhr5n/woman_baking_pie.jpg


Or was it backing? :smallannoyed: Damn, I forgot.

Awww, can I have a piece? <:(


We do not actually know the exact shape of the upper chamber or the lower chamber, and we do not actually know the exact shape or composition of the layer of stone/earth/whatever that separates the two.

Without that knowledge it is in fact impossible to say whether or not the physics are sound.

Yeah, the shape is critical. Stone would, assuming it's uniform, tend to dissipate the sound, but if the shape of the lower chamber focuses it, that might work to overcome the issues.

Then, maybe the stone isn't uniform which gets us back to our ear-trumpet/soundbox/etc. examples.

[Copperdragon]

We do not actually know the exact shape of the upper chamber or the lower chamber

We do. It is a flat ground.


and we do not actually know the exact shape or composition of the layer of stone/earth/whatever that separates the two.

We do not, but we do know it is - witout the shape/magic - thick enough to block screaming and also thick enough to "mostly" block a very hard strongly magical fist. So it is "solid stone" and "quite thick".
Thick enough to block normal speech of any kind unless it is somehow enhanced.


Without that knowledge it is in fact impossible to say whether or not the physics are sound.

It is. There is no known physical effect that would do what we have seen and the conclusion the physics is not sound is in line with what we have seen (blocked speech, blocked knocks).
It is rather simple, actually: If the stone is thin enough/transferring sound enough, it should be two-way. It is not, which means we know all about the material we have to.

I could imagine setups with holes etc, but those would not strong enough to let speech pass without any issues in one direction and basically block everything in the other.


Given what we do know, the only thing that can be said is that the physics are possible.

Given what we do know, the only thing that can be said is that the physics are highly implausible. Feel free to calculate the wave functions to convince me othervise.


And since similar effects already exist in the real, non-magic world, and there is no reason to believe that the physics that govern sound are any different in the OotS world (everything shown in the comic concerning sound without magic works exactly as it does in the real world), there is no reason to assume that the effect in the comic is anything but non-magical.

Where? Where is a one-way noise-cancellation-build through a stone wall that works up this level of perfection?


It is more parsimonious to assume that the Draketooths would choose to design such a simple thing physically than waste any magic on it, particularly in a Vancian magic system.

I use the same reasoning: Why waste a lot of effort on building a highly complex physical system that also opens a weak spot in your defense (thin enough walls) if you could just use trivial magic?
We're looking at a level 1 or level 2 spell enhanced with permanency here. That is very trivial if compared to the other magic in and around the pyramid. Also note this is a crucial point in the gate's defense (snooping on the people who already made it through).

[Chronos]

Quoth Amphiox:

It is quite possible to design acoustics that funnel sound waves in such a way as to make it so that sounds originating in location A are easy to hear in location B, but the reverse is not true.
It's quite possible to design them, but those designs won't work. In this house, we obey the laws of thermodynamics.

[warrl]

It's quite possible to design them, but those designs won't work. In this house, we obey the laws of thermodynamics.

So design one room to focus sound into the mouth of a sound-pipe of some sort.

Feed the other end of the sound-pipe into a second room designed to either focus sound *away* from the sound-pipe (possibly into a second sound-pipe that ends in an acoustically-dead space), or absorb/dissipate it.

Voila, one-way eavesdropping.

Do sound-pipes exist without magic? Yes they do. (https://en.wikipedia.org/wiki/Speaking_tube). Making one that is undetectable in a room that is all stone may require magical concealment, but that's a different question. And one could also ask whether a bunch of reasonably-high-power magicians might just use magic as their default first choice.

[Newwby]

There might be a bunch of pipe-like tunnels implanted between the two rooms that help with the acoustics? I don't know, I'm not knowledgeable in architecture.

If the positions were reversed and Roy was in the tunnel he could explain it to us. (http://www.giantitp.com/comics/oots0808.html)

[Boros Reckoner]

If the stone is thin enough/transferring sound enough, it should be two-way. It is not

You don't know that. V has "superior elven hearing", it's entirely plausible that the sound transfers both ways, but due to the shape of the chamber and V's hearing, he can hear the party while the party can't hear him



We're looking at a level 1 or level 2 spell enhanced with permanency here.

No, we're looking at a dead end with "acoustics designed for evesdropping on the chamber above it". That's how V said worded it, and if it were just a level 1 or 2 spell, he would have said that instead. I think he'd know the difference.

[Amphiox]

It's quite possible to design them, but those designs won't work. In this house, we obey the laws of thermodynamics.

The relevant laws are the laws of acoustics, not thermodynamics, and they flat out allow such designs to work.

I have experienced such an effect in the real world with my own ears, you know. I KNOW that it is possible.

[Amphiox]

We do. It is a flat ground.

The FLOOR is flat ground. But since the floor is in continuity with the walls and the whole room is capable of resonating, the shape that matters is the SHAPE OF THE WHOLE ROOM, and we do not know the exact shape of the whole room, only its general shape.





It is. There is no known physical effect that would do what we have seen and the conclusion the physics is not sound is in line with what we have seen (blocked speech, blocked knocks).
It is rather simple, actually: If the stone is thin enough/transferring sound enough, it should be two-way. It is not, which means we know all about the material we have to.

You are confusing "it should be two way" with "that therefore means that both V and the Order MUST hear the same sounds with same degree of ease".

That is not the case.



I could imagine setups with holes etc, but those would not strong enough to let speech pass without any issues in one direction and basically block everything in the other.

Holes are in fact not necessary.




Given what we do know, the only thing that can be said is that the physics are highly implausible. Feel free to calculate the wave functions to convince me othervise.

Again. I HAVE HEARD WITH MY OWN EARS THIS KIND OF EFFECT IN THE REAL WORLD. It does not require holes. It does not require pipes. It can work through thick stone.

This is like seeing that Bumblebee wings appear too small to allow them to fly, and then declaring that the physics therefore make it highly implausible for bumblebees to fly! But BUMBLEBEES DO FLY. We may not know exactly how the laws of physics are allowing them to fly, but because we observe that they do, we KNOW for a FACT that the laws of physics make it possible for them to fly.

So it is with this.

Again. The effect as described in the strip EXISTS IN THE REAL WORLD, and IT WORKS. No magic required.

You cannot deny that something is possible just because you cannot figure out how the physics of it should work, when IT EXISTS IN THE REAL WORLD and IT WORKS.

[Amphiox]

There are in fact more than one way this effect can be accomplished.

The easiest is this:

The floor acts like a diaphragm, transmitting sound (yes) BOTH WAYS. The transmission can be very faint, as befits thick rock, but that does not matter. It still works regardless.

The SHAPE of the rooms above and below results in resonance with the sound transmitted through the floor (which is faint) that AMPLIFIES that sound. If the shape is correct the amplification can be enormous. Even a very, very faint sound, transmitted very, very weakly, through very, very thick stone, can be amplified to the point where it can be heard.

The AMPLIFICATION is focused at a PARTICULAR POINT in each room. At that point the sound transmission, in both rooms is loudest. The transmission of sound between the rooms is two way BETWEEN THOSE TWO POINTS.

V is at or near the AMPLIFICATION POINT in her chamber. Roy and the others are NOT at or near the AMPLIFICATION POINT in their chamber. Thus V can hear Roy and the others easily, but Roy and the others cannot hear V easily. If they moved to the AMPLIFICATION POINT of their chamber, they would hear V equally easily. But probably that AMPLIFICATION POINT is suspended in mid-air twenty or thirty feet above their heads.

The simply fact that V is in the smaller room aids this effect enormously. The diaphragm that is the floor will transmit the sound energy equally into the two rooms. But as those vibrations resonate in each room, the equal energy is spread out over a much larger room in the case of Roy, Haley and Elan, and as a result the amount of sound energy that actually enters Roy's, Haley's, and Elan's ears is much less. Meanwhile, the equal energy is spread out over a much smaller room in V's case, and therefore the amount of sound energy that enters V's ears is comparatively MUCH GREATER.

This does not require any magic.

This does not require any magic.

This does not require any magic.

The only thing this depends on is the shape of the two rooms. The Giant, not being a acoustic physicist, may or may not have described the right shapes for the two rooms for it to work (and cleverly the Giant has chosen not to describe the shape of the two rooms entirely), but in principle it works and no magic is required.

No magic is required.

No magic is required.

No magic is required.

[Amphiox]

This same principle applies to all other forms of waves.

For example, light.

This is why you can look at someone through binoculars or a telescope and see them easily, while they, even if they look straight back at you, will not see you as easily, if at all, even though light goes both ways equally. The shape of the lenses and mirrors in your binoculars/telescope FOCUSES the light energy so that a lot of it gets into your eyes, but the person on the other end, without anything to focus the light energy, gets only a little bit of energy into his or her eyes, which is not enough for them to easily see you.

The amount of energy is the same and goes in both directions. But on one end it is conveniently FOCUSED into the observer's sense organ, while on the other it is not focused and remains diffuse.

Another example is tsunamis.

The same tsunami wave, radiating out from the epicenter in all directions, can hit the shore 100 miles away and BE FOCUSED by the shape of the coastline into a monstrous, destructive 20 foot wave, while 100 miles out in the other direction, in open sea, the same wave, with the same energy (same distance from the epicenter) is only 1 foot high and barely noticed by the yacht floating out there.

[rodneyAnonymous]

This is the Gate Room though, the final destination in a trap-filled labyrinth. And the people who set this up are very likely to consider magic solutions even before mundane ones, something we could have figured without Blackwing making an explicit reference to that tendency.

Whether or not it is possible to conceive an answer that doesn't involve magic, it is also possible (IMO probable!) that it does.

[F.Harr]

Again. I HAVE HEARD WITH MY OWN EARS THIS KIND OF EFFECT IN THE REAL WORLD. It does not require holes. It does not require pipes. It can work through thick stone.





There are in fact more than one way this effect can be accomplished.

The easiest is this:

The floor acts like a diaphragm, transmitting sound (yes) BOTH WAYS. The transmission can be very faint, as befits thick rock, but that does not matter. It still works regardless.

The SHAPE of the rooms above and below results in resonance with the sound transmitted through the floor (which is faint) that AMPLIFIES that sound. If the shape is correct the amplification can be enormous. Even a very, very faint sound, transmitted very, very weakly, through very, very thick stone, can be amplified to the point where it can be heard.

The AMPLIFICATION is focused at a PARTICULAR POINT in each room. At that point the sound transmission, in both rooms is loudest. The transmission of sound between the rooms is two way BETWEEN THOSE TWO POINTS.

V is at or near the AMPLIFICATION POINT in her chamber. Roy and the others are NOT at or near the AMPLIFICATION POINT in their chamber. Thus V can hear Roy and the others easily, but Roy and the others cannot hear V easily. If they moved to the AMPLIFICATION POINT of their chamber, they would hear V equally easily. But probably that AMPLIFICATION POINT is suspended in mid-air twenty or thirty feet above their heads.

The simply fact that V is in the smaller room aids this effect enormously. The diaphragm that is the floor will transmit the sound energy equally into the two rooms. But as those vibrations resonate in each room, the equal energy is spread out over a much larger room in the case of Roy, Haley and Elan, and as a result the amount of sound energy that actually enters Roy's, Haley's, and Elan's ears is much less. Meanwhile, the equal energy is spread out over a much smaller room in V's case, and therefore the amount of sound energy that enters V's ears is comparatively MUCH GREATER.

This does not require any magic.

This does not require any magic.

This does not require any magic.

The only thing this depends on is the shape of the two rooms. The Giant, not being a acoustic physicist, may or may not have described the right shapes for the two rooms for it to work (and cleverly the Giant has chosen not to describe the shape of the two rooms entirely), but in principle it works and no magic is required.

No magic is required.

No magic is required.

No magic is required.

All right, then. I buy it. Yes!

[Cavenskull]

All right, then. I buy it. Yes!
Excellent. That will be 20gp, please.

[Copperdragon]

V is at or near the AMPLIFICATION POINT in her chamber. Roy and the others are NOT at or near the AMPLIFICATION POINT in their chamber. Thus V can hear Roy and the others easily, but Roy and the others cannot hear V easily. If they moved to the AMPLIFICATION POINT of their chamber, they would hear V equally easily. But probably that AMPLIFICATION POINT is suspended in mid-air twenty or thirty feet above their heads.

This does not require any magic.

This does not require any magic.

This does not require any magic.

No magic is required.

No magic is required.

No magic is required.

Yessss, ok. Fine. Calm down, take a cookie. Go over there, sit down in that nice chair, enojy the nice day. All is fine, just please don't bite, yes?
And your caps-key seems to have a malfunction.

[Flame of Anor]

The floor acts like a diaphragm, transmitting sound (yes) BOTH WAYS. The SHAPE of the rooms above and below results in resonance with the sound transmitted through the floor (which is faint) that AMPLIFIES that sound. The AMPLIFICATION is focused at a PARTICULAR POINT in each room. At that point the sound transmission, in both rooms is loudest. The transmission of sound between the rooms is two way BETWEEN THOSE TWO POINTS. V is at or near the AMPLIFICATION POINT in her chamber. Roy and the others are NOT at or near the AMPLIFICATION POINT in their chamber. Thus V can hear Roy and the others easily, but Roy and the others cannot hear V easily. If they moved to the AMPLIFICATION POINT of their chamber, they would hear V equally easily. But probably that AMPLIFICATION POINT is suspended in mid-air twenty or thirty feet above their heads.

This does not require any magic.

This does not require any magic.

This does not require any magic.

The only thing this depends on is the shape of the two rooms. The Giant, not being a acoustic physicist, may or may not have described the right shapes for the two rooms for it to work (and cleverly the Giant has chosen not to describe the shape of the two rooms entirely), but in principle it works and no magic is required.

No magic is required.

No magic is required.

No magic is required.

http://25.media.tumblr.com/tumblr_m44jhlua4W1qmzo43o1_400.gif

[Coat]

Rig the roof of the gate room so that it reflects voices within the room down to the outside edge.

Cut a bunch of small holes all around the outside edge of the room. We can't see them, but they're small, so that might be an art artifact. Or you could hide them underneath a skirtingboard that runs round the bottom of the wall, but doesn't quite extend to the floor.

Under each hole, set up some kind of diaphragm that transfers the energy of the speech to a metal rod. Not my area of expertise, but seems like it could be done.

Run the rods down an arbitrary distance - I'd go for about 10 feet of stone - and connect them to a floating floor, underneath the dome that V is in. The floating floor is the speaker. You can hear the transferred sound normally in the passageway leading to the dome, but to get best reception you fly (designed by wizards, right?) to the focus point in the concave dome.

Technically speaking, this is still 2-way, but the diaphragms in the holes in the gate room are small and should provide very little amplification, plus you could design the roof to trap and absorb sound coming up from the edges of the room - which explains why the OotS' muttering when they were hiding behind the illusionary wall was not overheard by the linear guild.

You'll also note that V is careful not to step onto the floating floor directly under the dome. So this is clearly what the Giant had in mind when he drew it.

I don't actually have any training or knowledge about acoustics, so this could be a load of horse apples, but it seems like it might work?

A permanenced spell would probably still be easier though.

[F.Harr]

"Yessss, ok. Fine. Calm down, take a cookie. Go over there, sit down in that nice chair, enojy the nice day. All is fine, just please don't bite, yes?"

I've had days like that. When I was talked-down.

[Throknor]

At some point Girard had to hire architects (possibly dwarves), or have someone in the clan trained as an architect to design and build the ziggurat, or at least someone with Knowledge (Architecture and Engineering) (http://www.giantitp.com/comics/oots0808.html). It was Durokan's sthick to rely mainly on magic, and even he had dwarven builders. While Girard's is to rely on family, the best way for a family to survive on its own is to have differing expertises(sic).

There have already been physical traps that had to be engineered. Sound-proofed spy tunnels and one-way sound chambers can be added during the design phase just as easily.

[Chronos]

Acoustics, like all other branches of physics, must obey the laws of thermodynamics. And one consequence of the Second Law of Thermodynamics is that it is impossible to make a barrier that allows any form of energy through it more easily in one direction than the other. It is possible to create the illusion of this through various means (for instance, if the source on one side is louder than the source on the other, or if one side has more background noise), but a true one-way transmitter is not possible.

[DeliaP]

Acoustics, like all other branches of physics, must obey the laws of thermodynamics. And one consequence of the Second Law of Thermodynamics is that it is impossible to make a barrier that allows any form of energy through it more easily in one direction than the other. It is possible to create the illusion of this through various means (for instance, if the source on one side is louder than the source on the other, or if one side has more background noise), but a true one-way transmitter is not possible.

The 2nd law has a little bit more complexity (sure, you can't have one way valve, but you can have a pump if you put energy in) but that's still ok.

The issue here, though, is not the transmission of energy, but of information. These two properties are really only quite weakly linked (there's a stronger link between information and entropy, if we're being picky, but even that's not relevant here). So the 2nd law doesn't really say anything about the kind of acoustic trickery needed here.

What Amphiox is pointing out is that the signal on one side of a barrier could be focussed on a point, but on the other side could diffused. This would contradict neither the time reversibility of the laws of physics nor the irreversibility of the 2nd law of thermodynamics (I say nothing about whether there is a contradiction between those two points! :smallwink:)

Here's the simplest example I can think of, inspired by Amphiox: a large flat diaphragm. On one side, empty space. On the other side a large parabola shaped cave, with the open end capped by the diaphragm.

Vibrations of the diaphragm going to the empty space side spread out through normal wave diffusion processes.

Vibrations of the diaphragm going to the parabola size will (to first order) get reflected and focussed on the focal point of the parabola.

Now: someone whispers on the empty space side of the diaphragm. The whisper vibrates the diaphragm slightly, transmitting the sound to the other side. The sound wave in the parabola is focussed at the focal point. Someone standing at the focal point is likely to hear the whisper quite clearly. (Someone standing away from the focal point will not hear it well, as the sound wave is not focussed and is destructively interfereing).

Now what if someone inside the parabola is whispering? If they are away from the focal point, the parabola will cause destructive interference of the sound waves, and the diaphragm will vibrate with a very quiet noisy hum.

If they are at the focal point of the parabola, their whisper will be transmitted to the diaphragm coherently, and will cause the diaphragm to vibrate with their whisper. However, the sound wave on the emtpy space side will not be focussed, so the energy of the whisper is spread out across the empty space. For someone listening on the empty space side, the whisper will be much, much much quieter. Much much harder to hear. (But not impossible, so the knocking hand does make it through.)

The physics is reversible, energy is being transmitted equally well in either direction, and there is no violation of the 2nd law.

(More to the point, and as Amphiox points out, systems which do the acoustic trickery needed exist in the real world, so clearly cannot violate physics, including the 2nd law. QED. Yes, it is annoying when someone patronisingly tells you that you can't have seen that thing you saw because it's impossible.)

However: in response to the OP (!). Yes, the parabola seems to be the wrong way around! So OTOH the shape we are presented with in comic doesn't look like it's right to do the job by physics alone. TheYell and Colanderman's posts look a lot like what I've just described, though...

[AstralFire]

Call me crazy, but I like this sort of overanalysis (aware that it's not relevant or necessary to the comic, but an opportunity for an interesting science discussion) better than the usual semantic analysis.

[DeliaP]

Call me crazy, but I like this sort of overanalysis (aware that it's not relevant or necessary to the comic, but an opportunity for an interesting science discussion) better than the usual semantic analysis.

Alas, discussions on science forums can actually get even more flamey, because everyone believes that they can logically prove that they're right, about pretty much anything. :smallsigh:

[AstralFire]

Yes, I am not crazy about the all-capsing or the patronizing "calm down" interchange, but I thought I'd interject something positive.

[jere7my]

The issue here, though, is not the transmission of energy, but of information.

Well put. Here's another example (optical rather than acoustic):

Imagine I'm swimming in a pond, with my eyes about six inches below the surface. You're lying on the dock, thirty feet away. You can see me perfectly well, but because water has a greater index of refraction than air and I'm viewing the boundary at a glancing angle, I see what looks like a mirror. I can't see you at all.

[F.Harr]

I think part of the thing is, although the energy commng through is week, the shape of the room focuses it.

[Chronos]

Quoth DeliaP:

The 2nd law has a little bit more complexity (sure, you can't have one way valve, but you can have a pump if you put energy in) but that's still ok.

The issue here, though, is not the transmission of energy, but of information. These two properties are really only quite weakly linked (there's a stronger link between information and entropy, if we're being picky, but even that's not relevant here). So the 2nd law doesn't really say anything about the kind of acoustic trickery needed here.

What Amphiox is pointing out is that the signal on one side of a barrier could be focussed on a point, but on the other side could diffused. This would contradict neither the time reversibility of the laws of physics nor the irreversibility of the 2nd law of thermodynamics (I say nothing about whether there is a contradiction between those two points! )
This could work if one had a spatially-extended source, or an extended receiver, but both a humanoid mouth and a humanoid ear are small compared to the typical wavelength of sound, and so diffusion in one direction would also mean diffusion in the other direction.


Quoth jere7my:

Well put. Here's another example (optical rather than acoustic):

Imagine I'm swimming in a pond, with my eyes about six inches below the surface. You're lying on the dock, thirty feet away. You can see me perfectly well, but because water has a greater index of refraction than air and I'm viewing the boundary at a glancing angle, I see what looks like a mirror. I can't see you at all.
As a mental exercise, try drawing the ray diagram for the person on the dock viewing the person under the water. Now re-label which way the rays are going. Did your diagram change? If the line of sight is cut off one way, it'll be cut off the other, too.

[warrl]

The 2nd law has a little bit more complexity (sure, you can't have one way valve, but you can have a pump if you put energy in) but that's still ok.

One-way valves are commonplace in plumbing (https://en.wikipedia.org/wiki/Check_valve), electronics (https://en.wikipedia.org/wiki/Diode), and mechanics (https://en.wikipedia.org/wiki/Ratchet_(device)) - that I know of and thought of quickly.


Yes, it is annoying when someone patronisingly tells you that you can't have seen that thing you saw because it's impossible.

:smallbiggrin:

[jere7my]

As a mental exercise, try drawing the ray diagram for the person on the dock viewing the person under the water. Now re-label which way the rays are going. Did your diagram change? If the line of sight is cut off one way, it'll be cut off the other, too.

Sorry, but that's not true. Total internal reflection is possible when the first medium has a higher index of refraction than the second, but not vice versa.

http://en.wikipedia.org/wiki/Total_internal_reflection

To the person in the water (the higher-n material), the boundary at that angle looks like a mirror. To the person outside, it's completely transparent. You can try it yourself, next time you're at the pool.

[Cavenskull]

Sorry, but that's not true. Total internal reflection is possible when the first medium has a higher index of refraction than the second, but not vice versa.

http://en.wikipedia.org/wiki/Total_internal_reflection

To the person in the water (the higher-n material), the boundary at that angle looks like a mirror. To the person outside, it's completely transparent. You can try it yourself, next time you're at the pool.
It's not even necessary to use a swimming pool. An aquarium works fine for testing this and doesn't require getting wet. In a pinch, even a transparent glass half-full of water will work.

[jere7my]

It's not even necessary to use a swimming pool. An aquarium works fine for testing this and doesn't require getting wet. In a pinch, even a transparent glass half-full of water will work.

Okay, yes, but where I am right now getting into a pool sounds way better.

Happily, for the next eight days I'll be at a camp in the woods between two swimming ponds, and I'll have my mask and snorkel. Experiments ahoy!

[Cavenskull]

Okay, yes, but where I am right now getting into a pool sounds way better.

Happily, for the next eight days I'll be at a camp in the woods between two swimming ponds, and I'll have my mask and snorkel. Experiments ahoy!
Yeah, I definitely know what you mean! I only tossed out the alternatives for people who don't want to get wet. After all, people in the southern hemisphere probably aren't too concerned about trying to beat the heat right about now.

[Chronos]

Quoth jere7my:

Sorry, but that's not true. Total internal reflection is possible when the first medium has a higher index of refraction than the second, but not vice versa.
Yes, but you're assuming that both parties will be looking at the same angle. But the whole point of total internal reflection is that they won't be.

[Flame of Anor]

One-way valves are commonplace in plumbing (https://en.wikipedia.org/wiki/Check_valve), electronics (https://en.wikipedia.org/wiki/Diode), and mechanics (https://en.wikipedia.org/wiki/Ratchet_(device)) - that I know of and thought of quickly.


I think DeliaP was referring to Maxwell's Demon.

[jere7my]

Yes, but you're assuming that both parties will be looking at the same angle. But the whole point of total internal reflection is that they won't be.

Seriously, try it. To the person on the dock, there are no "blank spots" in the water. They can see the whole floor of the pond. The person in the water, on the other hand, can see directly above them, but most of their "ceiling" will look like a mirror. It's asymmetric. To the person on the dock, the image of the swimmer is shifted because the light is bent; to the person in the water, the image of the person on the dock can't even get to them.

[GreatWyrmGold]

It's definitely magic. There's solid stone above that little chamber, with no opening at all depicted. No matter what the shape of the chamber, the sound waves aren't going to propagate through stone miraculously just because the top of the chamber is domed. There would have to be some kind of air access, and there isn't any.

So, it's 100% magic. Maybe just some kind of ensorcelled stone that transmits sound in one direction?
My figurative money is on this. Girad was a sorcerer, not an architect, physicist, or methematician.

[Ghost Nappa]

My figurative money is on this. Girad was a sorcerer, not an architect, physicist, or methematician.

If Girard was a "methematician" we have more narrative problems on our hands then how acoustics work.

[littlebum2002]

I haven't taken a Physics class in over 10 years, but my money is on "it's possible".


Perhaps the artwork of the strip does not accurately demonstrate the design of the rooms which would allow this, but I don't see any reason it shouldn't work. I think the person had it right who said that, if the OOTS were in the right spot in their room, they would hear V clearly. The sound IS traveling in both directions, it's just getting focused in different places in each room. In the bottom room, the sound is focused where the person would be standing. Int he top room, the sound is focused near the top of the room, which is likely to be empty. Thus, the sound is not "traveling in one direction", but still allows one room to eavesdrop on another.



Also, I don't thing "Laird's Lugs" accurately describe the phenomena, either, because they're just holes in the wall

http://www.smashinglists.com/facts-about-the-edinburgh-castle/

[snikrept]

What is all this about "miraculous" nature of sound propagating through stone? Sound is going to travel easier through that stone, unless it has lots of cracks or discontinuities between different stone types. Sound propagates better through solids than gases.

The reason you can't hear well through walls is due to the air/wall interface on both sides of it (or the wall having other material discontinuities inside its structure -- thus acoustic dampening walls are made of foam or tile with tons of air/solid interfaces in it). It has nothing to do with sound waves somehow propagating in a weak manner through solids.

The eavesdropping setup would probably involve a Draketooth pressing his/her ear to the stone in the bottom chamber to maximize fidelity. Also, the shape of the roof in Roy's room is more important than the shape of the roof in V's room.

[Chronos]

Quoth jere7my:

Seriously, try it. To the person on the dock, there are no "blank spots" in the water. They can see the whole floor of the pond. The person in the water, on the other hand, can see directly above them, but most of their "ceiling" will look like a mirror. It's asymmetric. To the person on the dock, the image of the swimmer is shifted because the light is bent; to the person in the water, the image of the person on the dock can't even get to them.
Yes, the person in the water sees most of the surface as a near-perfect mirror. So? He doesn't need to see through those portions of the surface. If he looks up at an angle that's just barely steeper than the critical angle, then his line of sight will skim just above the surface of the water. The person in the pond can thus see everything outside the pond, just like the person outside the pond can see everything inside. Unless, of course, there's an obstacle in the way (the bottom of the dock, maybe), but in that case, the obstacle will block the sight of both.

Seriously, just draw the ray diagram. Take the ray diagram that shows the dry person seeing the wet person, and just reverse the direction of the arrows on the rays (you can do this because Snell's law is symmetric). The result will be a ray diagram which shows the wet person seeing the dry person.

[Throknor]

My figurative money is on this. Girad was a sorcerer, not an architect, physicist, or methematician.

He was an illusionist with ranger levels. Someone in the clan could have built the room. Do you think he magicked up the entire pyramid or built it? If built it, that required architecting and the room design would have been part of that.

Durokan was an Epic Wizard planning on using Epic Magic as his protection and he still hired dwarves for the design and construction of his fortress.

[GreatWyrmGold]

If Girard was a "methematician" we have more narrative problems on our hands then how acoustics work.
*grumbles about tyops*


He was an illusionist with ranger levels. Someone in the clan could have built the room. Do you think he magicked up the entire pyramid or built it? If built it, that required architecting and the room design would have been part of that.

Durokan was an Epic Wizard planning on using Epic Magic as his protection and he still hired dwarves for the design and construction of his fortress.
There are also mundane solutions to other problems he solved via magic, cough defense cough, and I was saying that because I felt there was a higher chance that Girard used magic, not a certain one. Especially because a magical solution would probably be simpler than an architectural one.

I noticed something about the discussion. It seems that it was assumed that the whatever-it-is blocked sound from V to the Order. While this was true, it was far from total--Haley heard V, even if it wasn't as well as vise versa. Food for thought.

[Warren Dew]

Acoustics, like all other branches of physics, must obey the laws of thermodynamics. And one consequence of the Second Law of Thermodynamics is that it is impossible to make a barrier that allows any form of energy through it more easily in one direction than the other. It is possible to create the illusion of this through various means (for instance, if the source on one side is louder than the source on the other, or if one side has more background noise), but a true one-way transmitter is not possible.
Exactly. If Roy & co. are away from the focal point in the upper chamber, they won't hear Vaarsuvius loudly, but Vaarsuvius won't hear them loudly either.

I think the background noise idea is a better explanation. One might expect that the upper chamber has a normal level of background noise, while the lower chamber is near silent. The lack of background noise would then allow Vaarsuvius to make out the sound from the upper chamber better.

[jere7my]

Yes, the person in the water sees most of the surface as a near-perfect mirror. So? He doesn't need to see through those portions of the surface. If he looks up at an angle that's just barely steeper than the critical angle, then his line of sight will skim just above the surface of the water. The person in the pond can thus see everything outside the pond, just like the person outside the pond can see everything inside. Unless, of course, there's an obstacle in the way (the bottom of the dock, maybe), but in that case, the obstacle will block the sight of both.

Seriously, just draw the ray diagram. Take the ray diagram that shows the dry person seeing the wet person, and just reverse the direction of the arrows on the rays (you can do this because Snell's law is symmetric). The result will be a ray diagram which shows the wet person seeing the dry person.

I hope this doesn't count as thread necromancy, but I've been in the woods for the last week.

While I was there, I happened to have a snorkel, an underwater camera, and some free time, and tested this experimentally. I held the camera under the still surface of the pond, pointed it at myself, and verified that I was able to see the lens when I took the picture. Here's the result:

http://farm3.staticflickr.com/2820/9330384573_9d83985c7c.jpg

As you can see, I could see it, but it couldn't see me (my eyes, anyway). Regardless of ray diagrams, real-world conditions can indeed make one-way information transmission possible.

Perhaps if I'd tilted the camera back a little, it would've been able to see me through the "hole" in the reflective surface of the water, and maybe it wouldn't've been too distorted to recognize me. But all we need to show here is that conditions can exist, for two fixed observers, such that A can see B's eyes (or lens) but B can't see A's, and that is very clearly the case here. If B is free to shift its line of sight around, things might be different.

[Chronos]

That's because you were aiming the camera in the wrong direction. You were aiming at the image of the underwater portion of your face. Your eyes were above the water, which put the image of your eyes in a different place.

[jere7my]

That's because you were aiming the camera in the wrong direction. You were aiming at the image of the underwater portion of your face. Your eyes were above the water, which put the image of your eyes in a different place.

No, I was pointing it directly at my eyes. They would be in the center of the image, if you could see them.

But that doesn't matter. All I have to demonstrate is that I could see the lens (which I could, very clearly) while it couldn't see my eyes. Sure, if the lens could move it might be able to see my eyes, but it didn't and couldn't. Sight is directional, not spherical. Given our relative positions, I could see everything about the camera, and it couldn't see (for instance) whether I had one eye closed. I could get information about it, but not vice-versa.

[F.Harr]

I say we move this discussion to Cecil Adams. All those in favor say yea (or aye, or whatever)!

[Flame of Anor]

I say we move this discussion to Cecil Adams. All those in favor say yea (or aye, or whatever)!

I say aye. Also, thank you for spelling "yea" correctly.

[F.Harr]

Well, yeah. I was going for formal parliamentary assent. ;)

Yay, I got one vote.

All those opposed say "nay".

[jere7my]

Well, yeah. I was going for formal parliamentary assent. ;)

Yay, I got one vote.

All those opposed say "nay".

Well, I just wanted to post my cool photo, so go ahead. :smallamused:

[F.Harr]

Hearing no objection, I take it that this is the unanimous will of the body. I guess I have to do this now, before someone moves to reconsider.

[F.Harr]

O.k., D-o-n-e.